The invention relates to a coolant circuit as well as to a method of operating a coolant circuit for a multi-cylinder internal-combustion engine having a cooling jacket surrounding a cylinder head housing and a cylinder block and supplied with cooling liquid by means of a pump.
A coolant circuit system of this type is known, for example, from European Patent Document EP 0 816 651 A1. A coolant circuit for an internal-combustion engine is described therein, in which the entire coolant flow is first guided through the cylinder head housing before it then flows through the cylinder block. So that the catalyst arranged in the exhaust system reaches its operating temperature as fast as possible after a cold start, the control of the coolant circuit is designed such that, below a coolant temperature T1, coolant flows only through the cylinder head housing and when T1 is reached, coolant also flows through the cylinder block.
In contrast, it is the object of the invention to implement by means of simple devices a coolant flow distribution which relates to the different temperature conditions in the cylinder block and the cylinder head of the internal-combustion engine and which meets the requirements.
According to the invention, this object is achieved by providing a coolant circuit for a multi-cylinder internal-combustion engine having a cooling jacket surrounding a cylinder head housing and a cylinder block and supplied with cooling liquid by means of a pump, characterized in that at least one cylinder cooling jacket and at least one cylinder head cooling space is provided with a connection for supplying the cooling liquid, and in that the flow of cooling fluid through the cylinder head housing and the cylinder block takes place in parallel. This objective is achieved by providing a method of operating a coolant circuit for a multi-cylinder internal-combustion engine, having a cooling jacket which surrounds a cylinder head housing and a cylinder block and which is supplied with cooling liquid by way of a pump, characterized in that the cooling liquid flows through the cylinder head housing and the cylinder block in parallel, that is simultaneously.
Additional advantageous further developments and improvements of the coolant circuit according to the invention are contained in the subclaims.
The coolant flow distribution, which meets the requirements, is coordinated by means of the cross-sections of the connections and/or by means of the flow resistances in the cooling jackets or cooling spaces such that approximately 70 to 80% of the coolant flow circulated for cooling the engine flows through the high-temperature-stressed cylinder head housing, while 20 to 30% is available for cooling the cylinder block.
The coolant advantageously flows transversely through the cylinder head housing. As a result, all cylinder head units are cooled optimally and uniformly. Distortions or component tensions in the cylinder head caused by temperature differences are reduced; a higher knock limit can be reached; whereby, in turn, the internal-combustion engine may have a higher compression.
Because of the fact that the coolant can flow transversely through the cylinder head housing, the connection for the cylinder head cooling space is connected with a longitudinal coolant duct which distributes the coolant uniformly to the individual cylinder head units by way of inlet openings provided at the longitudinal coolant duct.
The coolant circuit system according to the invention can be implemented in a simple and space-saving manner in that, on one side of a cylinder bank, one connection for the cylinder cooling jacket and one connection for a cylinder head cooling space are provided, while, on the other side, the cooling ducts of the cylinder cooling jacket and of the cylinder head cooling space lead by way of a common outlet into a return flow chamber.
It was found that, for cooling the cylinder blocks, it is sufficient that the cooling jacket for the cylinder block is constructed only in the upper area of the cylinder sides. The measure, which contributes to a further weight reduction, increases the efficiency of the internal-combustion engine and nevertheless ensures the required cooling of the temperature-stressed components of the internal-combustion engine.
An embodiment of the invention will be explained in detail in the following description and drawing.